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Cardiomyopathy is a group of primary diseases of the heart muscle. Early on there may be few or no symptoms. As the disease worsens, shortness of breath, feeling tired, and swelling of the legs may occur, due to the onset of heart failure. An irregular heart beat and fainting may occur. Those affected are at an increased risk of sudden cardiac death.
Hypertrophic cardiomyopathy is a condition in which muscle tissues of the heart become thickened without an obvious cause. The parts of the heart most commonly affected are the interventricular septum and the ventricles. This results in the heart being less able to pump blood effectively and also may cause electrical conduction problems. Specifically, within the bundle branches that conduct impulses through the interventricular septum and into the Purkinje fibers, as these are responsible for the depolarization of contractile cells of both ventricles.
Ventricular hypertrophy (VH) is thickening of the walls of a ventricle of the heart. Although left ventricular hypertrophy (LVH) is more common, right ventricular hypertrophy (RVH), as well as concurrent hypertrophy of both ventricles can also occur.
Restrictive cardiomyopathy (RCM) is a form of cardiomyopathy in which the walls of the heart are rigid. Thus the heart is restricted from stretching and filling with blood properly. It is the least common of the three original subtypes of cardiomyopathy: hypertrophic, dilated, and restrictive.
Disopyramide is an antiarrhythmic medication used in the treatment of ventricular tachycardia. It is a sodium channel blocker and is classified as a Class 1a anti-arrhythmic agent. Disopyramide has a negative inotropic effect on the ventricular myocardium, significantly decreasing the contractility. Disopyramide also has an anticholinergic effect on the heart which accounts for many adverse side effects. Disopyramide is available in both oral and intravenous forms, and has a low degree of toxicity.
Troponin C is a protein which is part of the troponin complex. It contains four calcium-binding EF hands, although different isoforms may have fewer than four functional calcium-binding subdomains. It is a component of thin filaments, along with actin and tropomyosin. It contains an N lobe and a C lobe. The C lobe serves a structural purpose and binds to the N domain of troponin I (TnI). The C lobe can bind either Ca2+ or Mg2+. The N lobe, which binds only Ca2+, is the regulatory lobe and binds to the C domain of troponin I after calcium binding.
Cardiac muscle troponin T (cTnT) is a protein that in humans is encoded by the TNNT2 gene. Cardiac TnT is the tropomyosin-binding subunit of the troponin complex, which is located on the thin filament of striated muscles and regulates muscle contraction in response to alterations in intracellular calcium ion concentration.
ACTC1 encodes cardiac muscle alpha actin. This isoform differs from the alpha actin that is expressed in skeletal muscle, ACTA1. Alpha cardiac actin is the major protein of the thin filament in cardiac sarcomeres, which are responsible for muscle contraction and generation of force to support the pump function of the heart.
The myosin-binding protein C, cardiac-type is a protein that in humans is encoded by the MYBPC3 gene. This isoform is expressed exclusively in heart muscle during human and mouse development, and is distinct from those expressed in slow skeletal muscle (MYBPC1) and fast skeletal muscle (MYBPC2).
Troponin C, also known as TN-C or TnC, is a protein that resides in the troponin complex on actin thin filaments of striated muscle and is responsible for binding calcium to activate muscle contraction. Troponin C is encoded by the TNNC1 gene in humans for both cardiac and slow skeletal muscle.
Myosin heavy chain, α isoform (MHC-α) is a protein that in humans is encoded by the MYH6 gene. This isoform is distinct from the ventricular/slow myosin heavy chain isoform, MYH7, referred to as MHC-β. MHC-α isoform is expressed predominantly in human cardiac atria, exhibiting only minor expression in human cardiac ventricles. It is the major protein comprising the cardiac muscle thick filament, and functions in cardiac muscle contraction. Mutations in MYH6 have been associated with late-onset hypertrophic cardiomyopathy, atrial septal defects and sick sinus syndrome.
Myosin essential light chain (ELC), ventricular/cardiac isoform is a protein that in humans is encoded by the MYL3 gene. This cardiac ventricular/slow skeletal ELC isoform is distinct from that expressed in fast skeletal muscle (MYL1) and cardiac atrial muscle (MYL4). Ventricular ELC is part of the myosin molecule and is important in modulating cardiac muscle contraction.
Atrial Light Chain-1 (ALC-1), also known as Essential Light Chain, Atrial is a protein that in humans is encoded by the MYL4 gene. ALC-1 is expressed in fetal cardiac ventricular and fetal skeletal muscle, as well as fetal and adult cardiac atrial tissue. ALC-1 expression is reactivated in human ventricular myocardium in various cardiac muscle diseases, including hypertrophic cardiomyopathy, dilated cardiomyopathy, ischemic cardiomyopathy and congenital heart diseases.
Hypertrophic cardiomyopathy screening is an assessment and testing to detect hypertrophic cardiomyopathy (HCM).
Ulrich Sigwart is a German retired cardiologist known for his pioneering role in the conception and clinical use of stents to keep blood vessels open, and introducing a non-surgical intervention, alcohol septal ablation for the treatment of hypertrophic obstructive cardiomyopathy.
Srihari S. Naidu is an American physician and Professor of Medicine at New York Medical College who is known for his work on hypertrophic cardiomyopathy including the procedure known as alcohol septal ablation, and for helping to construct the universal diagnostic criteria for cardiogenic shock.
Ischemic cardiomyopathy is a type of cardiomyopathy caused by a narrowing of the coronary arteries which supply blood to the heart. Typically, patients with ischemic cardiomyopathy have a history of acute myocardial infarction, however, it may occur in patients with coronary artery disease, but without a past history of acute myocardial infarction. This cardiomyopathy is one of the leading causes of sudden cardiac death. The adjective ischemic means characteristic of, or accompanied by, ischemia — local anemia due to mechanical obstruction of the blood supply.
D145E is a point mutation on troponin C that leads to hypertrophic cardiomyopathy disease. This mutation is caused by the change of nucleotide C to A at nucleotide 435, switching the amino acid aspartic acid to glutamic acid, which is located at the C-terminal tail. Patients with this mutation have different structure on the thin filament and alter the binding of Ca2+ at the troponin C site IV. Further, D145E causes increase in development of force and activation of ATPase in the presence of Ca2+.
Mavacamten, sold under the brand name Camzyos, is a medication used to treat obstructive hypertrophic cardiomyopathy.
Aficamten (CK-274) is a cardiac myosin inhibitor developed by Cytokinetics for the treatment of obstructive hypertrophic cardiomyopathy.
References
- ↑ Lehman, Sarah J.; Crocini, Claudia; Leinwand, Leslie A. (June 2022). "Targeting the sarcomere in inherited cardiomyopathies". Nature Reviews Cardiology. 19 (6): 353–363. doi:10.1038/s41569-022-00682-0. ISSN 1759-5010. PMC 9119933 .
- ↑ Sebastian, Sneha Annie; Padda, Inderbir; Lehr, Eric J.; Johal, Gurpreet (September 2023). "Aficamten: A Breakthrough Therapy for Symptomatic Obstructive Hypertrophic Cardiomyopathy". American Journal of Cardiovascular Drugs. 23 (5): 519–532. doi:10.1007/s40256-023-00599-0.
- ↑ Packard, Elizabeth; de Feria, Alejandro; Peshin, Supriya; Reza, Nosheen; Owens, Anjali Tiku (December 2022). "Contemporary Therapies and Future Directions in the Management of Hypertrophic Cardiomyopathy". Cardiology and Therapy. 11 (4): 491–507. doi: 10.1007/s40119-022-00283-5 . PMC 9652179 .